The present invention relates generally to an electronic engine tester and more particularly to an engine tester for determination and display of relative compression on a per cylinder basis.
It is well known in the art that relative compression is related to the current drawn by the starter motor during cranking. Essentially, current draw is representative of compression, as the starter motor requires more current to compress a well sealed cylinder than a poorly sealed cylinder.
There are presently available numerous relative compression measurement systems wherein starter current is monitored. One such system is described, in great detail, in U.S. Pat. No. 4,027,532, and the teachings thereof are incorporated herein by reference. The teachings of a related U.S. Pat. No. 4,125,894, are also incorporated herein as illustrating the sophisticated state of the art with respect to electronic engine testers. The present application and the incorporated patents are assigned to the Sun Electric Corporation of Chicago, Ill. (hereinafter "Sun Electric").
Unfortunately, the presently available systems do not display relative compression by cylinder. Although a per cylinder reading may be made and displayed, there is no correlation between the specific cylinders and the readings, such that additional tests and/or measurements must be performed to identify the problem cylinder.